I think a 150V varistor would preclude its use at 240V as it should short circuit the input, tripping the breaker and overheating the input wiring.

Unless it blows "open" instead, rendering itself useless right away while the remainder of the EVSE functions OK. That would be a technical design fault since its safety function is useless but who knows. I should pop open the case on my CMax EVSE at some point and snoop.

Varistors are more for surge suppression and momentary voltage spikes. If you apply 240V across a 150V varistor it will fail open in a rather incendiary fashion. In other words, the magic smoke found inside all electronics that make them work would leak out rendering it inoperable. Also I doubt very highly it would trip the 40A breaker on my 240V outlet.

Tomorrow I plan on modifying mine to make it dual voltage. Although I'm going to "cheat" a little and I'm sure UL would not approve! I'm separating the voltage going thru the relays and out to the car from the voltage supplied to the circuit board. The cheating part is I am going to use the ground as a neutral for the power supplying the circuit board. This is highly improper from an electrical wiring standpoint but it will work relatively safely.

This is possible because a 240V circuit isn't really a 240V circuit it is two 120V circuits. If you're not familiar with how household wiring works here's a readers digest explanation. A typical 120V circuit has 3 wires, a NEUTRAL, HOT, and GROUND (GND). A typical 240V circuit like my NEMA 6-50 outlet also has 3 wires, HOT, HOT, and GND. Some like a NEMA 14-50 outlet have a 4th wire which is a NEUTRAL. Each HOT is still only 120V. The trick to getting 240V from this is that between the two HOTs the AC sine waves are 180 degrees out of phase. What this means is that when one HOT is at +120V the other HOT is at -120V and measured between them you get 240V.

I have only used the OEM EVSE once and that was just to see if it worked. The only use I have for it is as a backup to my L2 EVSE should it ever fail. This would be bad since my FFE is my only car and there is no reasonable other way to charge my car but at home. If I can make the OEM EVSE into a 12A L2 it will be much more useful as a backup. I'll take pictures and post an explanation if anyone wants to copy and make their non-240V OEM EVSE more useful as a L1/L2 EVSE.

Tomorrow I plan on modifying mine to make it dual voltage. Although I'm going to "cheat" a little and I'm sure UL would not approve! I'm separating the voltage going thru the relays and out to the car from the voltage supplied to the circuit board. The cheating part is I am going to use the ground as a neutral for the power supplying the circuit board. This is highly improper from an electrical wiring standpoint but it will work relatively safely.

Good luck, let us know how it works out. What does your part number end with? -AF I'm guessing?

Just don't plug it into a GFCI circuit and you should be good. What is your 240v plug?

Good luck, let us know how it works out. What does your part number end with? -AF I'm guessing?

Per my previous posts, yes

cecil-t wrote:

Just don't plug it into a GFCI circuit and you should be good. What is your 240v plug?

Interesting the thought of plugging into a GFCI never crossed my mind, but you're right the way I'm wiring it it should trip a GFCI since I'm using the ground pin for current. I will try a GFCI outlet to see if it trips. I'm keeping the GFCI circuit on the EVSE intact for the power going to the car however by necessity the circuit board will be powered before the GFCI current transformer. As mentioned in my previous post, my 240V is a NEMA 6-50.

I'm working on it now. Just completed the hard part. Removing the relays.

I finished it. I replaced the plug with a NEMA 6-50 (240V). I already had a NEMA 6-50 to 5-15 adapter to plug into a regular 120V outlet that I use with my Juicebox EVSE. Post mod it worked on a 120V outlet. As expected it trips a GFCI 120V plug immediately. It appears to work just fine on 240V. here's a little 240V teaser:https://youtu.be/cer2TDnbOfwTomorrow or when I get around to it I'll do a write up with pictures in case anyone else want to try duplicating. I'll also get around to putting the case completely back together.

After several hours something went poof while charging. Tripped the 40A breaker. It left a nice black mark on my stool. I started doing a postmortem. I don't see anything obviously wrong but it looks like it was something with the relays(covered in carbon). The PCB sill looks fine. Sometime this week when I have time Ill see if I can figure out what went wrong.

I'm 90% sure the circuit board is still good. I still need to see if the relays are toast. I'll have to do some thinking about what I want to replace them with if they are toast. It almost looks like one or more of relays are what blew up but that wouldn't have tripped a breaker. My prime suspect is my soldering work on the bread board I soldered the relays to. It kind of boggles my mind that I don't see anywhere that there is an obvious short. FYI the relays were rated at 16A, 250V. If all else fails I can fall back on my original plan. for a little over 100 bucks I can replace all the internals with Open EVSE parts.

So there was a short on the breadboard I had mounted the relays too. Luckily it appears to have just arced on the breadboard between the two hot wires. I honestly couldn't tell exactly where it had arced. Just pretty much the whole board was toasty. My best guess is there was some slightly conductive residue on the board and the pads are very close together. With the right conditions eventually materializing it arced. I'm surprised the wires weren't melted considering it tripped a 40A breaker. I broke one of the relay pins off when I was removing them from the crispy bread board. I rigged it up with the relays "floating" just to make sure it still functioned. Tested on 120V first then plugged into 240V. I checked the current draw see below:Since I don't know the true condition of the relays I ordered two replacements and will update when they come in this weekend and I can do some more testing before I declare victory.